The present invention relates to a method and means for multiplexing signals from several optical sensors into a single signal receiver for subsequent processing. More particularly, this invention relates to a method and means for multiplexing signals from optical sensors which have their own light input optical fibers leading to the sensor, for carrying light, as well as their own signal output optical fibers leading away from the sensors, for carrying the output signal of the sensors.
In many industrial measurement applications there exists ambient conditions which make the ordinary electrical measurements using electrical sensors difficult or impossible. Such conditions include the presence of large electrical fields, which create noise pick-up in the electrical circuits normally connecting electrical sensors to centrallized instrumentation typical of idustrial applications. In order to overcome such pick-up problems optical sensors and optical communications are being used more frequently. These optical elements are immune to electrical pick-up and other troublesome ambient conditions.
In the industrial application of optical sensors it is frequently necessary to use large numbers of sensors; and, therefore, the instrumentation becomes expensive unless multiplexing of the sensor signals can be accomplished in a way which is inexpensive. Normally, when using electrical sensors, the multiplexing of the several sensor output signals to a common receiver which detects that output for further processing is an inexpensive approach. However, the multiplexing of optical signals has been difficult and expensive because of the inherent difficulties of commutating optical fibers in a manner similar to the commutating of electrical circuits.
It is an object of this invention to provide a method and means for commutating optical sensor signals without the need to commutate the fibers themselves.